A retrospective study was carried out of 195 patients having hemodynamic significant isolated acquired or congenital aortic stenosis (AS) undergoing aortic valve replacement (AVR) during 1962-1971 ("decade I") and 1972-1981 ("decade II"). Coronary artery disease did not exclude a patient from the study unless a left main lesion was present and simultaneous revascularization was not performed. In both decades the majority of patients were male but older by 10 years and less symptomatic in the second decade. No significant difference resulted in operative results, long-term survival, or complications comparing patients with acquired versus congenital AS. A variety of Starr-Edwards, Bjork-Shiley, and Hancock prostheses were used and complications were related to specific valve types. Operative mortality was higher the first decade, 16% vs. 3.4% the second. Cumulative follow-up was 995 years for both decades with good short and long-term symptomatic benefit resulting from AVR regardless of ventricular function or timing of operation. Long-term survival was similar at 5 years for both decades (65.8 plus or minus 5% and 71.7 plus or minus 6%) and was 59.1 plus or minus 5% at 10 years for first decade patients. Thromboembolism and anticoagulation complications were the most frequent clinical events following AVR. Of patients operated upon the first decade 73 plus or minus 5% were event free of thromboembolism at 5 years and 64 plus or minus 6% at 10 years; those operated upon the second decade, 76 plus or minus 6% were event free at 5 years. The incidence of freedom from an anticoagulation complication in the first decade was 89 plus or minus 4% at 5 years and 80 plus or minus 5% at 10 years; for those in the second, 87 1 plus or minus 5% at 5 years.